Rib Crowned Hamburgs ?

[David Love]

Now that you know they are rib crowned and not compression crowned, has
that changed you opinion of their tone quality?

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of Ric Brekne
Sent: Monday, June 20, 2005 12:18 AM
To: pianotech
Subject: Rib Crowned Hamburgs ?

Hi Folks

Just back from 2 weeks at the Hamburg Acadamy and just had to share with

one and all a most suprising experience I had whilst there.  As part of 
the acadamy cirriculum trainees are given a 3-4 hour long tour of the 
factory. Many fascinating elements of the Steinway Hamburg production 
methods were shown, and there was absolutely no discernable attempt to 
hide anything. We went through virtually every room in every production 
building and saw every stage of the production. 

In the course of the questions and discussions that took place underways

I (true to all previous adventures) jumped at the opportunity to ask 
about how Steinway soundboards are put together and I was told that in 
the Hamburg factory the panel is only dried to somewhere between 6 and 7

percent EMC before ribs were glued in place. I immediatly double 
questioned this and was assured this was, and always has been the case 
at Hamburg. The ribs are machine crowned and the caul is curved. So you 
have a mildly dried panel with machine crowned ribs pressed into a 
curved caul ! After expressing my suprise I was told that we would be 
viewing the soundboard assembly room in a little while.

The room itself  was rather small really. No sign of a hotbox anywhere. 
Curved ribs ready for installation were a plenty. Two glueing presses 
were clearly visable and tho I only caught a quick glimpse of these they

resembled the setup Terry Farrel posted pictures of a while back.  I 
asked once again about the panel EMC and lack of a hotbox and was told 
simply that the buildings are all held at a low enough RH to insure 6-7 
% EMC in all woods used for all production elements.

After the ribs were glued and dried for 6 hours, they trimmed (weakened)

the ends of the ribs which allowed the panel to curl up against the 
lessened holding power of the ribs where trimmed. This was said to 
create a kind of spring effect for the outer perimeter of the
soundboard.

There was a hotbox in another room for a much latter stage of 
production. This was when the entire assembly was to be fitted to the 
rim and the plate fitted in turn to both. The purpose for this hotbox 
was to insure maximum stability for thesoundboard assembly (including 
bridge) during this entire process.

Anyways, as this whole proceedure is essentially the same as pure rib 
crowning proceedures so enthusiastically debated back and forth on this 
list, I thought it would be interesting for you all to hear about it.

Cheers
RicB


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